Whole blood measurement method associated to hematocrit (hct) and whole blood measurement circuit thereof

ABSTRACT

A whole blood measurement method associated to hematocrit (HCT) and a whole blood measurement circuit thereof is applied in the detection of HCT of a whole blood sample to be tested. Herein, a time to digital converting circuit (TDC) is used for counting charging time or discharging time of a fixed capacitor and a to-be-tested sample, and a capacitance difference that is related to HCT is generated according to the charging time or the discharging time, so as to provide a reference for a whole blood feature test.

CROSS-REFERENCES TO RELATED APPLICATIONS

This non-provisional application claims priority under 35 U.S.C. §119(a)on Patent Application No. 105117886 filed in Taiwan, R.O.C. on Jun. 6,2016, the entire contents of which are hereby incorporated by reference.

BACKGROUND Technical Field

The present invention relates to a blood test technology, and inparticular, to a whole blood measurement method associated to hematocrit(HCT) and a whole blood measurement circuit thereof.

Related Art

In blood test procedures of common large hospitals or medical centers,first, blood cells are separated from plasma by using a centrifuge, andthen various types of tests are carried out on the plasma, so as toensure the accuracy of test results. A home detector performsmeasurement by directly using whole blood, and has advantages of lowblood volume, low cost, rapid detection, and portability. However, themeasurement performed by using whole blood causes that an error of acurrent blood glucose meter exceeds a standard, and accuracy of a bloodglucose test is reduced. May studies show that hematocrit (HCT) is avital factor that affects a blood glucose test.

HCT is the volume percentage of red blood cells in blood. Generally, theHCT of male blood is about 36% to 50%, and the HCT of female blood isabout 34% to 47%. People can know quality of blood according to the HCTin blood. When blood glucose concentration of blood is measured, ameasurement value of the blood glucose concentration also varies withthe HCT.

There are many methods for measuring the HCT, for example, the HCT maybe calculated by using an approach of measuring blood impedance, byusing an optical approach, by using a redox reaction approach, and byusing an electrochemical approach. Using a measurement method that usesa redox reaction approach as an example, in an electrochemical teststrip, a redox substance needs to be provided on a counter electrode, soas to generate an obvious redox current, thereby measuring the HCT.However, there is room for further improvement of the HTC measurementmethod in the prior art.

SUMMARY

In an embodiment, a whole blood measurement method associated tohematocrit (HCT) includes: counting a first charging time for charging afixed capacitor to a predetermined potential; converting the firstcharging time to a first digital signal by using a time to digitalconverting circuit (TDC); counting a second charging time for charging ato-be-tested sample to the predetermined potential; converting thesecond charging time to a second digital signal by using the TDC; andgenerating a capacitance difference according to the first digitalsignal, the second digital signal, and a capacitance of the fixedcapacitor.

In another embodiment, a whole blood measurement method associated toHCT includes: charging a fixed capacitor to a power supply potential byusing a power supply circuit;

counting a first discharging time for discharging the fixed capacitorfrom the power supply potential to a predetermined potential; convertingthe first discharging time to a first digital signal by using a TDC;charging a to-be-tested sample to the power supply potential by usingthe power supply circuit; counting a second discharging time fordischarging the to-be-tested sample from the power supply potential tothe predetermined potential; converting the second discharging time to asecond digital signal by using the TDC; and generating a capacitancedifference according to the first digital signal, the second digitalsignal, and a capacitance of the fixed capacitor.

In an embodiment, a whole blood measurement circuit associated to HCTincludes: a power supply circuit, a fixed capacitor, a first measurementend, a second measurement end, a charging switch, a first switch, asecond switch, a TDC, and a processing unit. The first measurement endand the second measurement end are configured to couple a to-be-testedsample. The charging switch is coupled between the power supply circuitand a first end of the fixed capacitor, and is coupled between the powersupply circuit and the first measurement end. The first switch iscoupled between a second end of the fixed capacitor and ground. Thesecond switch is coupled between the second measurement end and theground. The processing unit is coupled to the charging switch, the firstswitch, the second switch, and the TDC. The processing unit isconfigured to control the charging switch, the first switch, and thesecond switch so as to separately charge the fixed capacitor and theto-be-tested sample. The TDC is configured to count a first chargingtime for charging the fixed capacitor to a predetermined potential andconvert the first charging time to a first digital signal, and count asecond charging time for charging the to-be-tested sample to thepredetermined potential and convert the second charging time to a seconddigital signal. Then, the processing unit is further configured togenerate a capacitance difference according to the first digital signal,the second digital signal, and a capacitance of the fixed capacitor.

In another embodiment, a whole blood measurement circuit associated toHCT includes: a power supply circuit, a fixed capacitor, a firstmeasurement end, a second measurement end, a charging switch, a firstswitch, a second switch, a discharging resistor, a discharging switch, aTDC, and a processing unit. The first measurement end and the secondmeasurement end are configured to couple a to-be-tested sample. Thecharging switch is coupled between the power supply circuit and a firstend of the fixed capacitor, and is coupled between the power supplycircuit and the first measurement end. The first switch is coupledbetween a second end of the fixed capacitor and ground. The secondswitch is coupled between the second measurement end and the ground. Afirst end of the discharging resistor is coupled to the first end of thefixed capacitor and the first measurement end. The discharging switch iscoupled between a second end of the discharging resistor and the ground.The processing unit is coupled to the charging switch, the first switch,the second switch, the discharging switch, and the TDC. The processingunit is configured to control the charging switch, the first switch, thesecond switch, and the discharging switch so as to separately charge anddischarge the fixed capacitor and the to-be-tested sample. The TDC isconfigured to count a first discharging time for discharging the fixedcapacitor to a predetermined potential and convert the first dischargingtime to a first digital signal, and count a second discharging time fordischarging the to-be-tested sample to the predetermined potential andconvert the second discharging time to a second digital signal. Then,the processing unit is further configured to generate a capacitancedifference according to the first digital signal, the second digitalsignal, and a capacitance of the fixed capacitor.

To sum up, according to the embodiments, the whole blood measurementmethod associated to HCT and the whole blood measurement circuit thereofis applied in detection of HCT of a whole blood sample to be tested, soas to provide a calibration reference for a blood feature (e.g. bloodglucose) of a whole blood test, and further implement a blood test withlow blood volume, low cost, and high accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given herein below for illustration only, and thusare not limitative of the present invention, and wherein:

FIG. 1 is a schematic diagram of an embodiment of a whole bloodmeasurement circuit associated to hematocrit (HCT) according to thepresent invention;

FIG. 2 is a flowchart of a first embodiment of a whole blood measurementmethod associated to HCT according to the present invention;

FIG. 3 is a flowchart of an embodiment of step S310 in FIG. 2;

FIG. 4 is a flowchart of an embodiment of step S330 in FIG. 2;

FIG. 5 is a flowchart of a second embodiment of the whole bloodmeasurement method associated to HCT according to the present invention;

FIG. 6 is a flowchart of an embodiment of step S420 in FIG. 5;

FIG. 7 is a flowchart of an embodiment of step S450 in FIG. 5;

FIG. 8 is a flowchart of a third embodiment of the whole bloodmeasurement method associated to HCT according to the present invention;and

FIG. 9 is a flowchart of a fourth embodiment of the whole bloodmeasurement method associated to HCT according to the present invention.

DETAILED DESCRIPTION

FIG. 1 is a schematic diagram of an embodiment of a whole bloodmeasurement circuit associated to hematocrit (HCT) according to thepresent invention. Referring to FIG. 1, a whole blood measurementcircuit associated to HCT includes: a power supply circuit 110, a fixedcapacitor Cr, a first measurement end P1, a second measurement end P2, acharging switch Mp, a first switch Ml, a second switch M2, a processingunit 130, and a time to digital converting circuit (TDC) 150.

The charging switch Mp is coupled between the power supply circuit 110and a first end of the fixed capacitor Cr, and is coupled between thepower supply circuit 110 and the first measurement end P1. The firstswitch M1 is coupled between a second end of the fixed capacitor Cr andground G. The second switch M2 is coupled between the second measurementend P2 and the ground G. The processing unit 130 is coupled to thecharging switch Mp, the first switch M1, the second switch M2, and theTDC 150. In other words, a first end of the charging switch Mp iscoupled to a power supply end of the power supply circuit 110. A secondend of the charging switch Mp is coupled to the first end of the fixedcapacitor Cr and the first measurement end P1. A control end of thecharging switch Mp is coupled to the processing unit 130. A first end ofthe first switch M1 is coupled to the second end of the fixed capacitorCr. A second end of the first switch M1 is coupled to the ground G. Acontrol end of the first switch M1 is coupled to the processing unit130. A first end of the second switch M2 is coupled to the secondmeasurement end P2. A second end of the second switch M2 is coupled tothe ground G. A control end of the second switch M2 is coupled to theprocessing unit 130. In addition, the processing unit 130 iselectrically connected to the first end of the fixed capacitor Cr andthe first measurement end P1. During measurement, a to-be-tested sample20 is removably coupled between the first measurement end P1 and thesecond measurement end P2. At this time, the to-be-tested sample 20 isequivalent to a to-be-tested capacitor connected between the firstmeasurement end P1 and the second measurement end P2. In other words, anHCT change in blood (the to-be-tested sample 20) is equivalent to acapacitive effect.

FIG. 2 is a flowchart of a first embodiment of a whole blood HCTmeasurement method associated to HCT according to the present invention.FIG. 3 is a flowchart of an embodiment of step S310 in FIG. 2. FIG. 4 isa flowchart of an embodiment of step S330 in FIG. 2.

In an embodiment, referring to FIG. 1 to FIG. 4, the processing unit 130outputs control signals Sp and S1 to control the charging switch Mp andthe first switch M1 to be switched on (on), and simultaneously outputs astart signal S0 to the TDC 150 (step S311), so as to enable the powersupply circuit 110 to start charging the fixed capacitor Cr, and enablethe TDC 150 to start counting in response to the start signal S0 (stepS313). At this time, the second switch M2 is switched off. After thecharging switch Mp and the first switch M1 are switched on, the powersupply circuit 110 charges the fixed capacitor Cr via the chargingswitch Mp, and the TDC 150 simultaneously starts the counting. In acharging process, the processing unit 130 detects an end voltage of thefixed capacitor Cr (step S315), and determines whether the end voltagereaches a predetermined potential (hereinafter referred to as the firstpredetermined potential) (step S316). When the end voltage of the fixedcapacitor Cr does not reach the first predetermined potential, theprocessing unit 130 keeps outputting the control signals Sp and S1, soas to enable the charging switch Mp and the first switch M1 to maintainswitched on. When the end voltage of the fixed capacitor Cr reaches thefirst predetermined potential, the processing unit 130 outputs an endsignal St2 to the TDC 150 (step S317). At this time, the TDC 150 endsthe counting in response to the end signal St2, and obtains, on thebasis thereof, a first charging time for charging the fixed capacitor Crto the first predetermined potential (step S319). At this time, thefirst charging time is a time difference between a time for receivingthe start signal S0 and a time for receiving the end signal St2. The TDC150 converts the first charging time to a first digital signal Sc1 (stepS320) and transmits the first digital signal Sc1 to the processing unit130.

Besides, the processing unit 130 outputs control signals Sp and S2 tocontrol the charging switch Mp and the second switch M2 to be switchedon (on), and simultaneously outputs a start signal S0 to the TDC 150(step S331), so as to enable the power supply circuit 110 to startcharging the to-be-tested sample 20, and enable the TDC 150 to startcounting in response to the start signal S0 (step S333). At this time,the first switch M1 is switched off. After the charging switch Mp andthe second switch M2 are switched on, the power supply circuit 110charges the to-be-tested sample 20 via the charging switch Mp, and theTDC 150 simultaneously starts the counting. In a charging process, theprocessing unit 130 detects an end voltage of the to-be-tested sample 20(step S335), and determines whether the end voltage reaches the firstpredetermined potential (step S336). When the end voltage of theto-be-tested sample 20 does not reach the first predetermined potential,the processing unit 130 keeps outputting the control signals Sp and S2,so as to enable the charging switch Mp and the second switch M2 tomaintain switched on. When the end voltage of the to-be-tested sample 20reaches the first predetermined potential, the processing unit 130outputs an end signal St2 to the TDC 150 (step S337). At this time, theTDC 150 ends the counting in response to the end signal St2, andobtains, on the basis thereof, a second charging time for charging theto-be-tested sample 20 to the first predetermined potential (step S339).At this time, the second charging time is a time difference between atime for receiving the start signal S0 and a time for receiving the endsignal St2. The TDC 150 converts the second charging time to a seconddigital signal Sc2 (step S340) and transmits the second digital signalSc2 to the processing unit 130.

After receiving the first digital signal Sc1 and the second digitalsignal Sc2, the processing unit 130 generates a capacitance differenceaccording to the first digital signal, the second digital signal, and acapacitance of the fixed capacitor Cr (step S350). In some embodiments,a processing unit 130 may estimate a capacitance difference according achange between the first digital signal and the second digital signal,and a capacitance of the fixed capacitor Cr. At this time, the obtainedcapacitance difference is related to the HCT of the to-be-tested sample20.

In some embodiments, a first predetermined potential and a capacitanceof a fixed capacitor Cr are pre-stored in a storage unit (not shown inthe figures). When a processing unit 130 needs to use a value, theprocessing unit 130 reads, from the storage unit, the value that needsto be used (the first predetermined potential or the capacitance of thefixed capacitor Cr). The storage unit may be built in the processingunit 130, or may be located outside the processing unit 130 and iselectrically connected to the processing unit 130.

In some embodiments, a whole blood measurement circuit associated to HCTmay further include a discharging resistor Rr and a discharging switchMd. A first end of the discharging resistor Rr is coupled to a first endof a fixed capacitor Cr and a first measurement end P1. The dischargingswitch Md is coupled between a second end of the discharging resistor Rrand ground G. That is, a first end of the discharging switch Md iscoupled to the second end of the discharging resistor Rr. A second endof the discharging switch Md is coupled to the ground G. A control endof the discharging switch Md is coupled to a processing unit 130.

After each time when charging is completed, the processing unit 130outputs a control signal Sd to control the discharging switch Md to beswitched on (on), so as to discharge the charged fixed capacitor Cr orthe charged to-be-tested sample 20.

In another embodiment, a capacitance difference may be obtained bymeasuring a discharging time.

FIG. 5 is a flowchart of a second embodiment of the whole bloodmeasurement method associated to HCT according to the present invention.FIG. 6 is a flowchart of an embodiment of step S420 in FIG. 5. FIG. 7 isa flowchart of an embodiment of step S450 in FIG. 5.

In another embodiment, referring to FIG. 1 and FIG. 5 to FIG. 7, aprocessing unit 130 outputs control signals Sp and S1 to control acharging switch Mp and a first switch M1 to be switched on (on), so asto enable a power supply circuit 110 to start charging a fixed capacitorCr. At this time, both a second switch M2 and a discharging switch Mdare switched off. After the charging switch Mp and the first switch M1are switched on, the power supply circuit 110 charges the fixedcapacitor Cr via the charging switch Mp, so as to enable the fixedcapacitor Cr to be charged to a power supply potential (step S410). Insome embodiments, a processing unit 130 may control a time for charging,by a power supply circuit 110, a fixed capacitor Cr by controllingswitch on times of a charging switch Mp and a first switch M1, so as toenable the power supply circuit 110 to charge the fixed capacitor Cr toa power supply potential. For example, the processing unit 130 keepsoutputting control signals Sp and S1 for a predetermined time. Thepredetermined time is sufficient to enable the power supply circuit 110to charge the fixed capacitor Cr to the power supply potential. Theprocessing unit 130 stops outputting the control signals Sp and S1 afterthe predetermined time, so as to enable the charging switch Mp and thefirst switch M1 to be switched off (off). In some embodiments, aprocessing unit 130 may control a time for charging, by a power supplycircuit 110, a fixed capacitor Cr by detecting whether an end voltage ofthe fixed capacitor Cr reaches a power supply potential, so as tocontrol the power supply circuit 110 to charge the fixed capacitor Cr tothe power supply potential. For example, when the end voltage of thefixed capacitor Cr does not reach the power supply potential, theprocessing unit 130 keeps outputting control signals Sp and S1, so as toenable a charging switch Mp and a first switch M1 to maintain switchedon. When the end voltage of the fixed capacitor Cr reaches the powersupply potential, the processing unit 130 stops outputting the controlsignals Sp and S1, so as to enable the charging switch Mp and the firstswitch M1 to be switched off.

After the fixed capacitor Cr is charged to the power supply potential,the processing unit 130 outputs a control signal Sd to control thedischarging switch Md to be switched on (on), and simultaneously outputsa start signal S0 to the TDC 150 (step S421), so as to enable the fixedcapacitor Cr to be electrically connected to ground via the dischargingresistor Rr and the discharging switch Md and to be discharged, andenable the TDC 150 to start counting in response to the start signal S0(step S423). At this time, the charging switch Mp, the first switch M1,and the second switch M2 are all switched off. In a discharging process,the processing unit 130 detects an end voltage of the fixed capacitor Cr(step S425), and determines whether the end voltage reaches apredetermined potential (hereinafter referred to as the secondpredetermined potential) (step S426). When the end voltage of the fixedcapacitor Cr does not reach the second predetermined potential, theprocessing unit 130 keeps outputting the control signal Sd, so as toenable the discharging switch Md to maintain switched on. When the endvoltage of the fixed capacitor Cr reaches the second predeterminedpotential, the processing unit 130 outputs an end signal St2 to the TDC150 (step S427). At this time, the TDC 150 ends the counting in responseto the end signal St2, and obtains, on the basis thereof, a firstdischarging time for discharging the fixed capacitor Cr to the secondpredetermined potential (step S429). At this time, the first dischargingtime is a time difference between a time for receiving the start signalS0 and a time for receiving the end signal St2. The TDC 150 converts thefirst discharging time to a first digital signal Sc1 (step S430) andtransmits the first digital signal Sc1 to the processing unit 130.

Besides, the processing unit 130 outputs control signals Sp and S2 tocontrol the charging switch Mp and the second switch M2 to be switchedon (on), so as to enable the power supply circuit 110 to start chargingthe to-be-tested sample 20. At this time, both the first switch M1 andthe discharging switch Md are switched off. After the charging switch Mpand the second switch M2 are switched on, the power supply circuit 110charges the to-be-tested sample 20 via the charging switch Mp, so as toenable the to-be-tested sample 20 to be charged to the power supplypotential (step S440). In some embodiments, a processing unit 130 maycontrol a time for charging, by a power supply circuit 110, ato-be-tested sample 20 by controlling switch on times of a chargingswitch Mp and a second switch M2, so as to enable the power supplycircuit 110 to charge the to-be-tested sample 20 to a power supplypotential. For example, the processing unit 130 keeps outputting controlsignals Sp and S2 for a predetermined time. The predetermined time issufficient to enable the power supply circuit 110 to charge theto-be-tested sample 20 to the power supply potential. The processingunit 130 stops outputting the control signals Sp and S2 after thepredetermined time, so as to enable the charging switch Mp and thesecond switch M2 to be switched off (off). In some embodiments, aprocessing unit 130 may control a time for charging, by a power supplycircuit 110, a to-be-tested sample 20 by detecting whether an endvoltage of the to-be-tested sample 20 reaches a power supply potential,so as to control the power supply circuit 110 to charge the to-be-testedsample 20 to the power supply potential. For example, when the endvoltage of the to-be-tested sample 20 does not reach the power supplypotential, the processing unit 130 keeps outputting the control signalsSp and S2, so as to enable the charging switch Mp and the second switchM2 to maintain switched on. When the end voltage of the to-be-testedsample 20 reaches the power supply potential, the processing unit 130stops outputting the control signals Sp and S2, so as to enable thecharging switch Mp and the second switch M2 to be switched off.

After the to-be-tested sample 20 is charged to the power supplypotential, the processing unit 130 outputs a control signal Sd tocontrol the discharging switch Md to be switched on (on), andsimultaneously outputs a start signal S0 to the TDC 150 (step S451), soas to enable the to-be-tested sample 20 to be electrically connected toground via the discharging resistor Rr and the discharging switch Md andto be discharged, and enable the TDC 150 to start counting in responseto the start signal S0 (step S453). At this time, the charging switchMp, the first switch M1, and the second switch M2 are all switched off.In a discharging process, the processing unit 130 detects an end voltageof the to-be-tested sample 20 (step S455), and determines whether theend voltage reaches the second predetermined potential (step S456). Whenthe end voltage of the to-be-tested sample 20 does not reach the secondpredetermined potential, the processing unit 130 keeps outputting thecontrol signal Sd, so as to enable the discharging switch Md to maintainswitched on. When the end voltage of the to-be-tested sample 20 reachesthe second predetermined potential, the processing unit 130 outputs anend signal St2 to the TDC 150 (step S457). At this time, the TDC 150ends the counting in response to the end signal St2, and obtains, on thebasis thereof, a second discharging time for discharging theto-be-tested sample 20 to the second predetermined potential (stepS459). At this time, the second discharging time is a time differencebetween a time for receiving the start signal S0 and a time forreceiving the end signal St2. The TDC 150 converts the seconddischarging time to a second digital signal Sc2 (step S460) andtransmits the second digital signal Sc2 to the processing unit 130.

After receiving the first digital signal Sc1 and the second digitalsignal Sc2, the processing unit 130 generates a capacitance differenceaccording to the first digital signal, the second digital signal, and acapacitance of the fixed capacitor Cr (step S470). In some embodiments,a processing unit 130 may estimate a capacitance difference according achange between a first digital signal and a second digital signal, and acapacitance of a fixed capacitor Cr. At this time, the capacitancedifference is related to the HCT of the to-be-tested sample 20.

In some embodiments, a second predetermined potential and a capacitanceof a fixed capacitor Cr are pre-stored in a storage unit (not shown inthe figures). When a processing unit 130 needs to use a value, theprocessing unit 130 reads, from the storage unit, the value that needsto be used (the second predetermined potential or the capacitance of thefixed capacitor Cr). The storage unit may be built in the processingunit 130, or may be located outside the processing unit 130 and iselectrically connected to the processing unit 130.

FIG. 8 is a flowchart of a third embodiment of the whole bloodmeasurement method associated to HCT according to the present invention.FIG. 9 is a flowchart of a fourth embodiment of the whole bloodmeasurement method associated to HCT according to the present invention.

In some embodiments, after a capacitance difference is obtained, aprocessing unit 130 may further convert the capacitance difference to acorresponding HCT value (step S360 or step S480), as shown in FIG. 8 andFIG. 9. In some embodiments, a processing unit 130 may convert acapacitance difference to a corresponding HCT value on the basis of acomparison table, a conversion curve, or a conversion formula. Thecomparison table, the conversion curve, or the conversion formula may bepre-stored in a storage unit (not shown in the figures).

It should be understood that execution sequences of steps are notlimited to exemplary sequences shown in the drawings, the executionsequences may be appropriately adjusted according to execution contentof the steps without departing from the spirit and scope of the presentinvention. For example: the counting of the charging time (ordischarging time) of the to-be-tested sample is executed at first, andthen the counting of the charging time (or discharging time) of thefixed capacitor is executed. Alternatively, the counting of the chargingtimes (or discharging times) of the fixed capacitor and the to-be-testedsample can be simultaneously executed by using two groups of circuits.

In some embodiments, a to-be-tested sample 20 may be a blood glucosetest strip. A processing unit 130 may be a microprocessor, amicrocontroller, a digital signal processor, a micro-computer, a centralprocessing unit, a field programmable gate array, a programmable logicdevice, a state machine, a logic circuit, an analog circuit, a digitalcircuit, and/or any apparatus for operating a signal (analog and/ordigital) based on an operation instruction. The foregoing storage unitmay be implemented by one or more storage elements. At this time, astorage element may be a memory, a working storage, or the like, forexample, but is not limited herein.

To sum up, according to the embodiments, the whole blood measurementmethod associated to HCT and the whole blood measurement circuit thereofis applied in detection of HCT of a whole blood sample to be tested, soas to provide a calibration reference for a blood feature (e.g. bloodglucose) of a whole blood test, and further implement a blood test withlow blood volume, low cost, and high accuracy.

While the present disclosure has been described by way of example and interms of the preferred embodiments, it is to be understood that theinvention needs not be limited to the disclosed embodiments. For anyoneskilled in the art, various modifications and improvements within thespirit of the instant disclosure are covered under the scope of theinstant disclosure. The covered scope of the instant disclosure is basedon the appended claims.

What is claimed is:
 1. A whole blood measurement method associated tohematocrit (HCT), comprising: counting a first charging time forcharging a fixed capacitor to a predetermined potential; converting thefirst charging time to a first digital signal by using a time to digitalconverting circuit (TDC); counting a second charging time for charging ato-be-tested sample to the predetermined potential; converting thesecond charging time to a second digital signal by using the TDC; andgenerating a capacitance difference according to the first digitalsignal, the second digital signal, and a capacitance of the fixedcapacitor.
 2. The whole blood measurement method associated to HCTaccording to claim 1, further comprising: converting the capacitancedifference to a corresponding HCT value.
 3. The whole blood measurementmethod associated to HCT according to claim 1, wherein the step ofcounting a first charging time for charging a fixed capacitor to apredetermined potential comprises: switching on a charging switch andoutputting a start signal to the TDC; starting the counting in responseto the start signal by using the TDC; charging the fixed capacitor byusing a power supply circuit via the charging switch; detecting an endvoltage of the fixed capacitor; outputting an end signal to the TDC whenthe end voltage reaches the predetermined potential; and ending thecounting in response to the end signal by using the TDC, and obtainingthe first charging time for charging the fixed capacitor to thepredetermined potential, wherein the first charging time is a timedifference between a time for receiving the start signal and a time forreceiving the end signal.
 4. The whole blood measurement methodassociated to HCT according to claim 1, wherein the step of counting asecond charging time for charging a to-be-tested sample to thepredetermined potential comprises: switching on a charging switch andoutputting a start signal to the TDC; starting the counting in responseto the start signal by using the TDC; charging the to-be-tested sampleby using a power supply circuit via the charging switch; detecting anend voltage of the to-be-tested sample; outputting an end signal to theTDC when the end voltage reaches the predetermined potential; and endingthe counting in response to the end signal by using the TDC, andobtaining the second charging time for charging the to-be-tested sampleto the predetermined potential, wherein the second charging time is atime difference between a time for receiving the start signal and a timefor receiving the end signal.
 5. The whole blood measurement methodassociated to HCT according to claim 1, wherein the to-be-tested sampleis a blood glucose test strip.
 6. A whole blood measurement methodassociated to HCT, comprising: charging a fixed capacitor to a powersupply potential by using a power supply circuit; counting a firstdischarging time for discharging the fixed capacitor from the powersupply potential to a predetermined potential; converting the firstdischarging time to a first digital signal by using a TDC; charging ato-be-tested sample to the power supply potential by using the powersupply circuit; counting a second discharging time for discharging theto-be-tested sample from the power supply potential to the predeterminedpotential; converting the second discharging time to a second digitalsignal by using the TDC; and generating a capacitance differenceaccording to the first digital signal, the second digital signal, and acapacitance of the fixed capacitor.
 7. The whole blood measurementmethod associated to HCT according to claim 6, further comprising:converting the capacitance difference to a corresponding HCT value. 8.The whole blood measurement method associated to HCT according to claim6, wherein the step of counting a first discharging time for dischargingthe fixed capacitor from the power supply potential to a predeterminedpotential comprises: switching on a discharging switch and outputting astart signal to the TDC; starting the counting in response to the startsignal by using the TDC; electrically connecting the fixed capacitor toground by using the discharging switch to discharge; detecting an endvoltage of the fixed capacitor; outputting an end signal to the TDC whenthe end voltage reaches the predetermined potential; and ending thecounting in response to the end signal by using the TDC, and obtainingthe first discharging time for discharging the fixed capacitor to thepredetermined potential, wherein the first discharging time is a timedifference between a time for receiving the start signal and a time forreceiving the end signal.
 9. The whole blood measurement methodassociated to HCT according to claim 6, wherein the step of counting asecond discharging time for discharging the to-be-tested sample from thepower supply potential to the predetermined potential comprises:switching on a discharging switch and outputting a start signal to theTDC; starting the counting in response to the start signal by using theTDC; electrically connecting the to-be-tested sample to ground by usingthe discharging switch to discharge; detecting an end voltage of theto-be-tested sample; outputting an end signal to the TDC when the endvoltage reaches the predetermined potential; and ending the counting inresponse to the end signal by using the TDC, and obtaining the seconddischarging time for discharging the to-be-tested sample to thepredetermined potential, wherein the second discharging time is a timedifference between a time for receiving the start signal and a time forreceiving the end signal.
 10. The whole blood measurement methodassociated to HCT according to claim 6, wherein the to-be-tested sampleis a blood glucose test strip.
 11. A whole blood measurement circuitassociated to HCT, comprising: a power supply circuit; a fixedcapacitor; a first measurement end; a second measurement end, configuredto couple a to-be-tested sample along with the first measurement end; acharging switch, coupled between the power supply circuit and a firstend of the fixed capacitor, and coupled between the power supply circuitand the first measurement end; a first switch, coupled between a secondend of the fixed capacitor and ground; a second switch, coupled betweenthe second measurement end and the ground; a TDC, configured to count afirst charging time for charging the fixed capacitor to a predeterminedpotential and convert the first charging time to a first digital signal,and count a second charging time for charging the to-be-tested sample tothe predetermined potential and convert the second charging time to asecond digital signal; and a processing unit, coupled to the chargingswitch, the first switch, the second switch, and the TDC, configured tocontrol the charging switch, the first switch, and the second switch soas to separately charge the fixed capacitor and the to-be-tested sample,and configured to generate a capacitance difference according to thefirst digital signal, the second digital signal, and a capacitance ofthe fixed capacitor.
 12. The whole blood measurement circuit associatedto HCT according to claim 11, wherein the processing unit is furtherconfigured to convert the capacitance difference to a corresponding HTCvalue.
 13. The whole blood measurement circuit associated to HCTaccording to claim 11, wherein the to-be-tested sample is a bloodglucose test strip.
 14. A whole blood measurement circuit associated toHCT, comprising: a power supply circuit; a fixed capacitor; a firstmeasurement end; a second measurement end, configured to couple ato-be-tested sample along with the first measurement end; a chargingswitch, coupled between the power supply circuit and a first end of thefixed capacitor, and coupled between the power supply circuit and thefirst measurement end; a first switch, coupled between a second end ofthe fixed capacitor and ground; a second switch, coupled between thesecond measurement end and the ground; a discharging resistor, wherein afirst end of the discharging resistor is coupled to the first end of thefixed capacitor and the first measurement end; a discharging switch,coupled between a second end of the discharging resistor and ground; aTDC, configured to count a first discharging time for discharging thefixed capacitor to a predetermined potential and convert the firstdischarging time to a first digital signal, and count a seconddischarging time for discharging the to-be-tested sample to thepredetermined potential and convert the second discharging time to asecond digital signal; and a processing unit, coupled to the chargingswitch, the first switch, the second switch, the discharging switch, andthe TDC, configured to control the charging switch, the first switch,the second switch, and the discharging switch so as to separately chargeand discharge the fixed capacitor and the to-be-tested sample, andconfigured to generate a capacitance difference according to the firstdigital signal, the second digital signal, and a capacitance of thefixed capacitor.
 15. The whole blood measurement circuit associated toHCT according to claim 14, wherein the processing unit is furtherconfigured to convert the capacitance difference to a corresponding HTCvalue.
 16. The whole blood measurement circuit associated to HCTaccording to claim 14, wherein the to-be-tested sample is a bloodglucose test strip.